For plethysmographic studies of respiratory mechanics, we selected, from a general population, 51 subjects, aged 25-75 yr, who had never smoked, had no present or past cardiorespiratory symptoms or disease, were alpha1-antitrypsin MM phenotypes, and were normal by physical examination, vectorcardiography, and chest roentgenography. Approximately equal numbers of men and women were represented in each of three age groups; 25-35, 36-64, and 65-75. Both sexes demonstrated loss of lung elastic recoil with age, most significant at high lung volumes, but the rate of loss was less than previously reported. Males had higher lung recoil than females of comparable age, but if lung size was taken into account, there were no sex differences in bulk elastic properties. Maximum expiratory flow diminished with age only at low volumes, suggesting that equal pressure points are more centrally located at low lung volumes in the elderly.